|Publication number||US5907420 A|
|Application number||US 08/713,568|
|Publication date||May 25, 1999|
|Filing date||Sep 13, 1996|
|Priority date||Sep 13, 1996|
|Also published as||CA2215115A1, CA2215115C, DE69732203D1, DE69732203T2, EP0829981A2, EP0829981A3, EP0829981B1|
|Publication number||08713568, 713568, US 5907420 A, US 5907420A, US-A-5907420, US5907420 A, US5907420A|
|Inventors||Andrew R. Chraplyvy, John C. Ellson, George W. Newsome, Robert William Tkach, John Lehrer Zyskind|
|Original Assignee||Lucent Technologies, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (17), Non-Patent Citations (16), Referenced by (50), Classifications (14), Legal Events (9)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
The present invention relates generally to optical fiber communication networks and, more particularly, to systems and methods for dynamically controlling gain in accordance with the collective behavior of the amplifier chains employed in the links of such networks.
2. Description of the Background Art
A dramatic increase in the information capacity of an optical fiber can be achieved by the simultaneous transmission of optical signals over the same fiber from many different light sources having properly spaced peak emission wavelengths. By operating each light source at a different peak wavelength, the integrity of the independent messages from each source is maintained for subsequent conversion to electric signals at the receiving end. This is the basis of wavelength division multiplexing (WDM).
Wavelength switched optical networks potentially offer high capacity networking at lower cost than current electronically switched networks. The optical amplifiers in the nodes and repeaters of such networks will each be traversed by multiple signal channels following diverse routes. In optical amplifiers such as rare-earth doped fiber amplifiers (e.g., erbium doped fiber amplifiers--EDFA's), amplified spontaneous emission (ASE) is the major source of noise. ASE originates from the spontaneous emission of incoherent light over the broad gain bandwidth of the amplifier and constitutes the random noise contribution of the amplifier. If the signal powers in the transmission fibers are too high, optical nonlinearities such as Stimulated Brillouin Scattering (SBS) can also occur and further degrade the signals by introducing noise. In the wavelength domain, gain saturation induced by a data channel operating at λ1 produces a level change in another data channel at wavelength λ2.
In optically amplified systems, the above-described noise sources present two limitations on the amplifier operating range. At low input signal levels the amplifier random noise contribution, ASE, causes bit errors (signal-spontaneous beat noise) while at large input signal levels, nonlinearities in the transmission fiber add noise and can also degrade performance. As such, fluctuations in the transmitted data stream--as may occur, for example, when one or more wavelength channels are added or dropped--can have a substantial effect on the reliability and quality of service in a multiwavelength network. Illustratively, the number of channels traversing an EDFA may change suddenly as a result of a network reconfiguration or a fault that interrupts some of the channels. Cross saturation in the affected optical amplifiers of a network will induce power transients in the surviving channels, the speed of which is proportional to the number of amplifiers in the network; for large networks, surviving channel power transients can be large and extremely fast. If their power levels exceed thresholds for optical nonlinearities or become too low to preserve adequate eye opening, the surviving channels traversing the optical amplifier will suffer error bursts.
The gain medium in a rare-earth doped optical fiber amplifier such, for example, as an EDFA has a comparatively long excited state lifetime or relaxation time, and for this reason is generally regarded as allowing for a larger saturation energy and, hence, as exhibiting virtually no saturation in response to high speed data pulses (1 ns). In fact, it has been reported that transient effects of gain saturation and recovery in an individual amplifier typically occur on a 100 μsec-1 msec time scale. Desurvire et al., Erbium Doped Fiber Amplifiers, p. 412 (1994)!. The inventors herein, have, however, observed gain dynamics in a chain of EDFA's almost two orders of magnitude faster than this and, for large scale wavelength routed networks, gain dynamics three orders of magnitude may be predicted. These fast transients in chains of amplifiers may ultimately constrain the design or extent of multiwavelength optical networks. Accordingly, there is recognized a need for a technique by which the amplifiers employed in optical networks can be reliably controlled despite power level fluctuations in the respective wavelength channels or, in the case of time division multiplexed networks, individual time slots.
The aforementioned need is addressed, and an advance is made in the art, by a system and method of protecting, on a link-by-link basis, the surviving channels in a link between wavelength routing network elements (NE's). According to the invention, an optical control channel is added before a plurality of optical amplifiers in a link. To prevent improper loading of downstream links, the control channel is stripped off at the next wavelength routing network element. The power of the control channel is automatically adjusted using a fast feedback circuit to hold substantially constant the total power of the signal channels and the control channel at the input of the first amplifier. In this manner, channel loading of all optical amplifiers in the link is maintained substantially constant, and the incidence of error bursts, as might otherwise result when one or more channels are added or dropped due to a network fault or reconfiguration, is substantially reduced.
The above features and advantages of the present invention will become apparent from the ensuing description of several preferred exemplary embodiments, which should be read in conjunction with the accompanying drawings, in which:
FIG. 1 is a block diagram depicting a portion of an illustrative optical network employing chains of optical amplifiers and link control in accordance with the present invention;
FIG. 2 is a block diagram of an investigative apparatus utilized to evaluate the effectiveness of link control in accordance with the present invention;
FIG. 3 is a graphical representation of the wavelength channel spectrum obtained at the link control power tap in the investigative apparatus of FIG. 2;
FIG. 4 is a graphical representation comparing the bit error rates obtained with and without link control in accordance with the present invention while six or seven multiple wavelength channels were transmitted over the 560 km transmission span employed in the investigative apparatus of FIG. 2; and
FIG. 5 is a graphical representation comparing the power excursions observed in a surviving wavelength channel, with and without the control channel operating to maintain constant power over the test transmission span.
An illustrative, large-scale optical communications network 10 is shown in FIG. 1. Initially, it should be noted that although a wavelength division multiplexed (WDM) network is shown and described in detail, such description is by way of illustrative example only. It should, in fact, be readily appreciated by those skilled in the art from the discussion which follows that the teachings of the present invention are equally applicable to other multiplexed optical networks such, for example, as time division multiplexed (TDM) networks.
In any event, and as seen in FIG. 1, wavelength division multiplexed data is transmitted on multiple wavelengths or channels between a plurality of network routing elements--illustratively, cross-connect switches (XC)--that are distributed throughout the network 10 and interconnected by optical fiber links. Although an optical communications network such as network 10 may, in fact, include hundreds of such network routing elements, only three such switches--indicated generally at 12a, 12b, and 12c--are shown for purposes of clarity and ease of illustration.
With continued reference to FIG. 1, it will be observed that the optical fiber links between a pair of network elements, as for example, link 14 that interconnects cross-connect switches 12a and 12c, typically includes many optical amplifiers--these being indicated generally at 16a through 16n. The type and spacing of the optical amplifiers employed along the link will, of course, depend upon the wavelength band to be utilized for transmission. A typical wavelength band of interest in telecommunications applications, for example, is centered at 1550 nm. The gain profile of a rare-earth doped fiber amplifier (EDFA) is generally regarded as being best suited for this wavelength, with a typical inter-amplifier spacing of 40 km being considered suitable for an optical fiber link such as link 14.
Essentially, the present invention is based on the recognition by the inventors herein that the gain dynamics in a chain of optical amplifiers such, for example, as the erbium doped fiber amplifiers (EDFA's) deployed in link 14 of network 10, may be up to several orders of magnitude faster than those reported for a single amplifier. According to the present invention, a technique for maintaining constant input power to all of the amplifiers in a link is utilized to ensure continued reliable service, in the surviving channels being transmitted along the link, when one or more wavelength channels are suddenly dropped or added, as may be experienced when a system reconfiguration or fault occurs.
In the illustrative embodiment of the invention depicted in FIG. 1, link control according to the present invention is implemented by a feedback arrangement that includes a power tap 18, a photodetector 20, a control circuit 22 that responds to fluctuations in the transmitted power level detected by the photodetector 20 by adjusting an output error signal which, in turn, controls the output power level of optical source 24--illustratively a semiconductor laser--which outputs a control signal at a wavelength λc that is within the gain band of the optical amplifier. The thus generated control channel λc is then introduced back into the link as, for example, by a wavelength selective coupler 26. As will be readily appreciated by those skilled in the art, by controlling the power level of the control channel, it is possible to maintain the power level of the optical signal supplied to some or all of the optical amplifiers in a given link (depending, of course, upon where the control channel is introduced). In the illustrative embodiment of FIG. 1, the feedback control circuit is implemented before the first amplifier (amplifier 16a) so that the optical power input to all of the optical amplifiers is maintained at a substantially constant level.
Preferably, the control channel is stripped off at the next wavelength routing NE to prevent improper loading of downstream links. This is easily achieved either by addition of another filter or as a byproduct of the filtering action of the demultiplexers commonly located in NEs. Advantageously, the amplifiers between wavelength routing NE's require no special control circuitry or modification since control is handled on a link-by-link basis.
An experimental setup for the demonstration of link control surviving channel power protection is illustrated in FIG. 2. The outputs of seven tunable lasers tuned to MONET channel wavelengths as shown were combined, five through a fused fiber coupler and the other two through a second coupler, and each group was amplified. The output of the five lasers was passed through an acousto-optic modulator to simulate the loss and addition of these channels and then combined with the other pair in a 2×2 coupler. The channels were then modulated at 2.5 Gb/s.
The link control channel (λc =1554 nm) was then added before the first amplifier in the link using a circulator and Bragg grating. A spectrum showing the signal channels and control channel when all channels are present is shown in FIG. 3. In an actual system, the grating Bragg wavelength should be chosen close to, but outside of, the band of signal channels so as to permit use of the full complement of signal channels. A portion of the total power of the signal channels and the control channels was tapped off and detected. A fast feedback circuit was used to adjust the line control channel's power to maintain the total power constant. The signal channels and control channel were then transmitted through seven amplified spans of standard single mode fiber with a total length of 570 km and passed through a bandpass filter to select channel 7, the bit error rate of which was monitored.
Measurements were carried out in which all seven signal channels were transmitted and in which channels 1, 2, 3, 5, 7 and 8 were transmitted. When channels 1, 2, 3, 5 and 8 were modulated on and off with a frequency of 1 KHz (FIG. 4) surviving channel 7 suffers a penalty exceeding 2 dB for seven channel transmission (two surviving channels) and 3 dB for six channel transmission (one surviving channel) due to the induced cross saturation. Finally, measurements were carried out with the control channel operating to maintain constant power through the link. The results of these measurements are shown in FIG. 5. Without control, channel 7 suffers large power excursions which degrade the BER performance due to optical nonlinearities in the transmission fiber. With fast link control according to the present invention in operation, on the other hand, the power excursions are mitigated. The feedback circuit utilized in the investigational apparatus of FIG. 2 limits the power increase after 4 μs; a faster circuit would limit the power excursions even more effectively. Even with the present control circuit, Channel 7 is successfully protected (see FIG. 4); penalties are reduced to a few tenths of a dB and the error floors disappear.
As will be readily ascertained by those skilled in the art, the link control technique of the present invention is fast; changes in channel loading result in prompt changes in a link's total power--permitting much faster detection and response than schemes which rely on detecting the much slower changes in channel output power, gain or ASE in individual EDFA's (which are much slower than the transients in EDFA networks). Performing corrections on a per link basis rather than a per amplifier basis simplifies the required hardware, does not increase the complexity of the network's EDFA's and is well suited to the architecture of wavelength routed networks.
An additional benefit of link control according to the present invention is the cancellation of modulation of the total power arising from the information content of the signal channels. The faster transient response of long chains of amplifiers will result in cross talk due to cross saturation in the amplifier chains up to much higher frequencies than would occur for single amplifiers, as high as 10 MHz for large networks. The link control channel eliminates this crosstalk by eliminating modulation in the total power for the range of frequencies at which cross saturation will occur. Other advantages include detection of changes in channel loading, speed limited only by feedback circuit, simpler implementation requiring less hardware, less management and no changes to the amplifiers and cancellation of low frequency channel power variations.
From the foregoing, it should be readily ascertained by those skilled in the art that the invention is not limited by the embodiments described above which are presented herein as examples only but may, in fact, be modified in various ways within the scope of protection as defined by the appended patent claims.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US5225922 *||Nov 21, 1991||Jul 6, 1993||At&T Bell Laboratories||Optical transmission system equalizer|
|US5311347 *||Jun 30, 1992||May 10, 1994||Fujitsu Limited||Optical communication system with automatic gain control|
|US5374973 *||Sep 21, 1993||Dec 20, 1994||Alcatel Network Systems, Inc.||Optical amplifier|
|US5396360 *||May 11, 1994||Mar 7, 1995||Canon Kabushiki Kaisha||Wavelength-multiplexed optical communication system and optical amplifier used therefor|
|US5428471 *||Jul 30, 1992||Jun 27, 1995||Alcatel Network Systems, Inc.||Fail-safe automatic shut-down apparatus and method for high output power optical communications system|
|US5438445 *||Oct 29, 1991||Aug 1, 1995||Hitachi, Ltd.||Optical wavelength multiplexing communication system|
|US5448660 *||Jul 6, 1994||Sep 5, 1995||Cselt - Centro Studi E Laboratori Telecomunicazioni S.P.A.||Wavelength selective optical switch|
|US5463487 *||Jul 29, 1994||Oct 31, 1995||Northern Telecom Limited||Optical transmission system|
|US5479082 *||Jul 6, 1994||Dec 26, 1995||Cselt-Centro Studi E Laboratorti Telecommunicazioni S.P.A.||Device for extraction and re-insertion of an optical carrier in optical communications networks|
|US5488500 *||Aug 31, 1994||Jan 30, 1996||At&T Corp.||Tunable add drop optical filtering method and apparatus|
|US5500756 *||Feb 26, 1993||Mar 19, 1996||Hitachi, Ltd.||Optical fiber transmission system and supervision method of the same|
|US5510926 *||Jan 11, 1995||Apr 23, 1996||Alcatel N.V.||Transmission method and an optical link using multiplexing with application|
|US5633741 *||Feb 23, 1995||May 27, 1997||Lucent Technologies Inc.||Multichannel optical fiber communications|
|US5644423 *||Mar 13, 1996||Jul 1, 1997||Nec Corporation||Method and device for optical amplification|
|US5673142 *||Aug 1, 1996||Sep 30, 1997||Lucent Technologies Inc.||Optical amplifier with internal input signal monitoring tap|
|US5675432 *||Apr 3, 1996||Oct 7, 1997||Hitachi, Ltd.||Optical amplification apparatus|
|US5701186 *||Mar 29, 1996||Dec 23, 1997||Ciena Corporation||Optical cable TV system|
|1||A. Hamel et al, "Optical filters in WDM Ring Network Architectures" Proc. SPIE, vol. 2449, pp. 70-77 Int. Soc. Opt. Eng. 1995.|
|2||*||A. Hamel et al, Optical filters in WDM Ring Network Architectures Proc. SPIE, vol. 2449, pp. 70 77 Int. Soc. Opt. Eng. 1995.|
|3||H. Toba et al "An Optical FDM-Based Self-Healing Ring Network Employing Arrayed Waveguide Grating Filters and EDFA's with Level Equalizers", IEEE J. on Selected Areas in Communications, V. 14, #5, Jun., 1996 pp. 800-813.|
|4||*||H. Toba et al An Optical FDM Based Self Healing Ring Network Employing Arrayed Waveguide Grating Filters and EDFA s with Level Equalizers , IEEE J. on Selected Areas in Communications, V. 14, 5, Jun., 1996 pp. 800 813.|
|5||J.E. Midwinter, Photonics in Switching vol. II Systems Academic Press, "Quantum Electronics-Principles and Applications" Chap. 3.|
|6||*||J.E. Midwinter, Photonics in Switching vol. II Systems Academic Press, Quantum Electronics Principles and Applications Chap. 3.|
|7||L. Quetel et al "Programmable fiber grating based wavelength multiplexer" OFC '96 Technical Digest, WF6, pp. 120-121.|
|8||*||L. Quetel et al Programmable fiber grating based wavelength multiplexer OFC 96 Technical Digest, WF6, pp. 120 121.|
|9||N. N. Khrais et al "Effect of cascaded misaligned optical (de) (de) multiplexers on multiwavelength optical network performance" OFC '96 Technical Digest pp. 220-221.|
|10||*||N. N. Khrais et al Effect of cascaded misaligned optical (de) (de) multiplexers on multiwavelength optical network performance OFC 96 Technical Digest pp. 220 221.|
|11||*||Oda et al, An Optical FDM Add/Drop Myltiplexing Ring Network Utilizing Fiber Fabry Perot Filters and Optical Circulators, IEEE Photo. Tech. Letters, vol. 5, No. 7, pp. 825 828, Jul. 1993.|
|12||Oda et al, An Optical FDM-Add/Drop Myltiplexing Ring Network Utilizing Fiber Fabry-Perot Filters and Optical Circulators, IEEE Photo. Tech. Letters, vol. 5, No. 7, pp. 825-828, Jul. 1993.|
|13||P.A. Perrier et al. "4-channel, 10-Gbit/s capacity self-healing WDM ring network with wavelength add/drop multiplexers". OFC '96 Technical Digest, ThD3, pp. 218-220.|
|14||*||P.A. Perrier et al. 4 channel, 10 Gbit/s capacity self healing WDM ring network with wavelength add/drop multiplexers . OFC 96 Technical Digest, ThD3, pp. 218 220.|
|15||P.E. Green, Jr., "Optical Networking Update", IEEE J. of Selected Areas in Communications. vol. 14, #5, Jun. 1996 pp. 764-779.|
|16||*||P.E. Green, Jr., Optical Networking Update , IEEE J. of Selected Areas in Communications. vol. 14, 5, Jun. 1996 pp. 764 779.|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US6142994 *||May 5, 1998||Nov 7, 2000||Ep Technologies, Inc.||Surgical method and apparatus for positioning a diagnostic a therapeutic element within the body|
|US6169615 *||Mar 13, 1998||Jan 2, 2001||Fujitsu Limited||Wavelength division multiplex optical transmission apparatus|
|US6275313 *||Feb 3, 1998||Aug 14, 2001||Lucent Technologies Inc.||Raman gain tilt equalization in optical fiber communication systems|
|US6342959 *||Sep 24, 1997||Jan 29, 2002||Alcatel||Transient suppression in an optical wavelength division multiplexed network|
|US6388802||Jul 31, 2001||May 14, 2002||Seneca Networks||Reduction of ASE in WDM optical ring networks|
|US6400475 *||Nov 12, 1998||Jun 4, 2002||Hitachi, Ltd.||Optical transmission system and optical communications device|
|US6421168||Jan 3, 2002||Jul 16, 2002||Seneca Networks||Reduction of ASE in WDM optical ring networks|
|US6426817 *||Jan 26, 1999||Jul 30, 2002||Fujitsu Limited||Optical wavelength multiplexing system and terminal|
|US6456408 *||Mar 22, 1999||Sep 24, 2002||Lucent Technologies Inc.||Method and apparatus for controlling the optical power of a optical transmission signal|
|US6563614||May 21, 1999||May 13, 2003||Corvis Corporation||Optical transmission system and amplifier control apparatuses and methods|
|US6584246 *||Jul 5, 2000||Jun 24, 2003||Litton Systems, Inc.||Source, system and method for generating amplified stimulated emission using a coupler mechanism|
|US6671466||Jul 20, 1999||Dec 30, 2003||Lucent Technologies Inc.||Distortion compensation in optically amplified lightwave communication systems|
|US6678041 *||Jun 1, 2001||Jan 13, 2004||Advantest Corporation||Optical characteristic measuring apparatus, the method thereof and recording medium|
|US6760152||Oct 11, 2002||Jul 6, 2004||Jds Uniphase Corporation||Method for increasing dynamic range of erbium doped fiber amplifiers|
|US6907195||Aug 28, 2001||Jun 14, 2005||Dorsal Networks, Inc.||Terminals having sub-band substitute signal control in optical communication systems|
|US6907201 *||Jul 28, 2000||Jun 14, 2005||Ciena Corporation||Optical power transient control system and method|
|US6944399||Aug 28, 2001||Sep 13, 2005||Dorsal Networks, Inc.||Methods of signal substitution for maintenance of amplifier saturation|
|US7016104||Jun 30, 2003||Mar 21, 2006||Jds Uniphase Corporation||Wider dynamic range to a FBG stabilized pump|
|US7054559 *||Sep 4, 1997||May 30, 2006||Mci Communications Corporation||Method and system for modular multiplexing and amplification in a multi-channel plan|
|US7072588 *||Aug 17, 2001||Jul 4, 2006||Halliburton Energy Services, Inc.||Multiplexed distribution of optical power|
|US7106487 *||Jun 25, 2003||Sep 12, 2006||Intel Corporation||Thermal tuning of a laser using doped silicon etalon|
|US7173756||Feb 17, 2005||Feb 6, 2007||Jds Uniphase Corporation||Optical amplification system for variable span length WDM optical communication systems|
|US7181137 *||Sep 30, 2002||Feb 20, 2007||Cisco Technology, Inc.||Subband spectrum analysis for optical multiplex section protection|
|US7327958 *||Jul 30, 2004||Feb 5, 2008||Lucent Technologies Inc.||Transient-based channel growth for optical transmission systems|
|US7349637||Dec 1, 2006||Mar 25, 2008||Optium Corporation||Optical transmitter with SBS suppression|
|US7529482||Jan 18, 2007||May 5, 2009||Cisco Technology, Inc.||Subband spectrum analysis for optical multiplex section protection|
|US7738791||Jan 21, 2004||Jun 15, 2010||Ericsson, Ab||Transmitter and method for transmitting messages on an optical fiber|
|US7822345||Jan 21, 2004||Oct 26, 2010||Ericsson Ab||Output stage for carrying out WDM message transmission and methods for exchanging full light sources in an output stage of this type|
|US7903978||Mar 8, 2011||Broadwing, Llc||Optical transmission systems and amplifier control apparatuses and methods|
|US8064770 *||Nov 22, 2011||Tyco Electronics Subsea Communications Llc||System and method for spectral loading an optical transmission system|
|US8462428||Jan 12, 2009||Jun 11, 2013||Nokia Siemens Networks Oy||Method and device for providing and/or controlling an optical signal|
|US8705978 *||Jun 20, 2011||Apr 22, 2014||Futurewei Technologies, Inc.||Method of efficiently and safely adding and deleting channels in an amplified wavelength division multiplexing system|
|US8965202 *||Dec 4, 2012||Feb 24, 2015||Fujitsu Limited||Optical power monitor, optical power control system and optical power monitor method|
|US20030048502 *||Aug 28, 2001||Mar 13, 2003||Zhengchen Yu||Methods of signal substitution for maintenance of amplifier saturation|
|US20030048508 *||Aug 28, 2001||Mar 13, 2003||Zhengchen Yu||Terminals having sub-band substitute signal control in optical communication systems|
|US20040036956 *||Jun 30, 2003||Feb 26, 2004||Jds Uniphase Corporation||Wider dynamic range to a FBG stabilized pump|
|US20050012984 *||Jun 25, 2003||Jan 20, 2005||Balaji Venkateshwaran||Thermal tuning of a laser using doped silicon etalon|
|US20050031343 *||Sep 8, 2004||Feb 10, 2005||Stephens Thomas D.||Optical transmission system and amplifier control apparatuses and methods|
|US20060024057 *||Jul 30, 2004||Feb 2, 2006||Kilper Daniel C||Transient-based channel growth for optical transmission systems|
|US20060051093 *||Aug 11, 2005||Mar 9, 2006||Massimo Manna||System and method for spectral loading an optical transmission system|
|US20060177221 *||Jan 21, 2004||Aug 10, 2006||Marconi Communitions Gmbh||Transmitter and method for transmitting messages on an optical fiber|
|US20060193035 *||Feb 17, 2005||Aug 31, 2006||Optovia Corporation||Optical Amplification System For Variable Span Length WDM Optical Communication Systems|
|US20060263089 *||Jan 21, 2004||Nov 23, 2006||Cornelius Furst||Output stage for carrying out wdm message transmission and methods for exchanging full light sources in an output stage of this type|
|US20070086779 *||Dec 7, 2006||Apr 19, 2007||Broadwing Corporation||Optical transmission systems and amplifier control apparatuses and methods|
|US20080075469 *||Dec 1, 2006||Mar 27, 2008||Optium Corporation||Optical transmitter with sbs suppression|
|US20110051228 *||Jan 12, 2009||Mar 3, 2011||Nokia Siemens Networks Oy||Method and device for providing and/or controlling an optical signal|
|US20120321319 *||Dec 20, 2012||Futurewei Technologies, Inc.||Method of Efficiently and Safely Adding and Deleting Channels in an Amplified Wavelength Division Multiplexing System|
|US20130251365 *||Dec 4, 2012||Sep 26, 2013||Fujitsu Limited||Optical power monitor, optical power control system and optical power monitor method|
|DE10303313A1 *||Jan 28, 2003||Jul 29, 2004||Marconi Communications Gmbh||Message transmission method via optical fiber, by distributing change in optical power of filling channels to reduce displacement of entire spectrum|
|DE10303314A1 *||Jan 28, 2003||Jul 29, 2004||Marconi Communications Gmbh||Output stage for wavelength division multiplexing transmission, has auxiliary circuit for supplying one of two filling light sources with continuously decreasing desired-power signal|
|U.S. Classification||398/180, 398/37, 398/38, 398/97, 398/94, 398/30|
|International Classification||H04B10/04, H04B10/14, H04B10/16, H04J14/02, H04B10/17, H04B10/06|
|Dec 23, 1996||AS||Assignment|
Owner name: AT&T CORP., NEW YORK
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:CHRAPLYVY, ANDREW R.;ELLSON, JOHN C.;NEWSOME, GEORGE W.;AND OTHERS;REEL/FRAME:008324/0056;SIGNING DATES FROM 18961218 TO 19961205
Owner name: LUCENT TECHNOLOGIES, NEW JERSEY
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:CHRAPLYVY, ANDREW R.;ELLSON, JOHN C.;NEWSOME, GEORGE W.;AND OTHERS;REEL/FRAME:008324/0056;SIGNING DATES FROM 18961218 TO 19961205
|Apr 5, 2001||AS||Assignment|
Owner name: THE CHASE MANHATTAN BANK, AS COLLATERAL AGENT, TEX
Free format text: CONDITIONAL ASSIGNMENT OF AND SECURITY INTEREST IN PATENT RIGHTS;ASSIGNOR:LUCENT TECHNOLOGIES INC. (DE CORPORATION);REEL/FRAME:011722/0048
Effective date: 20010222
|Nov 27, 2001||CC||Certificate of correction|
|Sep 30, 2002||FPAY||Fee payment|
Year of fee payment: 4
|Nov 3, 2006||FPAY||Fee payment|
Year of fee payment: 8
|Dec 6, 2006||AS||Assignment|
Owner name: LUCENT TECHNOLOGIES INC., NEW JERSEY
Free format text: TERMINATION AND RELEASE OF SECURITY INTEREST IN PATENT RIGHTS;ASSIGNOR:JPMORGAN CHASE BANK, N.A. (FORMERLY KNOWN AS THE CHASE MANHATTAN BANK), AS ADMINISTRATIVE AGENT;REEL/FRAME:018590/0047
Effective date: 20061130
|Nov 19, 2010||FPAY||Fee payment|
Year of fee payment: 12
|Mar 7, 2013||AS||Assignment|
Owner name: CREDIT SUISSE AG, NEW YORK
Free format text: SECURITY INTEREST;ASSIGNOR:ALCATEL-LUCENT USA INC.;REEL/FRAME:030510/0627
Effective date: 20130130
|Oct 9, 2014||AS||Assignment|
Owner name: ALCATEL-LUCENT USA INC., NEW JERSEY
Free format text: RELEASE BY SECURED PARTY;ASSIGNOR:CREDIT SUISSE AG;REEL/FRAME:033950/0001
Effective date: 20140819